Cable assemblies comprising a hollow, flexible conduit and a wire slidably retained within the conduit are used in many applications where it is desired to transfer a linear, push/pull type of motion between remotely located elements of a mechanism. Cable end fittings are used to connect the ends of the conduit to relatively fixed structures, usually closely adjacent to the point where the wire is attached to the connected elements. Such cable assemblies and end fittings are commonly used in mechanisms such as automotive window regulators, throttle actuator assemblies, and automatic transmission shift linkages.
When a cable assembly is initially installed in its operating environment, the length of the wire is adjusted to be greater than the length of its surrounding conduit by an amount necessary for proper functioning of the mechanism. Although the wire would ideally be perfectly taut, a certain amount of slack in the wire must be included in the design to allow for manufacturing tolerances. During use, the wire is placed in tension so that some amount of stretching or elongation of the cable inevitably takes place. Simultaneously, the conduit is subjected to compression and so shortens by some small amount. Eventually the wire becomes too long relative t the conduit, such that the amount of slack in the wire is greater than the designed-for amount and consequently the cable assembly is unable to transfer linear motion with the degree of accuracy required for the mechanism in question. Excessive slack in the wire is of particular importance in certain mechanical applications, such as electronically controlled powered window regulators having an auto-reverse function.
End fittings which automatically correct for increases in the amount of slack in a cable assembly are known. One example of such an end fitting is disclosed in U.S. Pat. No. 5,746,094.